When Entergy Corp. announced plans to shut down its Vermont Yankee nuclear plant in August 2013, Wendell filmmaker Robbie Leppzer had already been filming his documentary for 3½ years.

Leppzer, whose latest film, “Power Struggle” chronicles the conflicts over the Vernon, Vt. reactor’s relicensing, will be screened in an Oct. 23 “sneak preview” 2 p.m. showing at the Academy of Music in Northampton, as well as a Nov. 3 showing at the Latchis Theater in Brattleboro, Vt.

The 104-minute film, for which Leppzer is trying to raise $100,000 for post-production work, will be aired on HBO sometime next year, says the documentary filmmaker. He also received support from NHK, the Japanese Broadcasting Corporation.

Leppzer has directed dozens of independent film, video, and public radio documentaries for national and international distribution for more than 35 years. He says he considered making a film about Vermont Yankee in anticipation of the plant’s operating license expiration in March 2012.

The Nuclear Regulatory Commission was set to renew the plant’s operating license, but Vermont’s unique state authority as well over nuclear power licenses, separate from those issued by the NRC, made this neighboring plant a riveting subject for the filmmaker, who’d begun his career after Hampshire College with a 1977 film about the occupation of the Seabrook nuclear plant then being built.

Entergy bought Vermont Yankee in 2002, agreeing to the Vermont Public Service Board’s authority to consider a “public good” certificate for the license to keep operating, but in 2006, the state gave its Legislature say on whether the Board would even get to decide.

In early January 2010, when Leppzer heard that anti-nuclear activists planned to walk 126 miles from Brattleboro to lobby the Vermont Legislature in Montpelier over 11 days in the dead of winter, he knew it was time to begin filming.

Little did he expect that a few days into the walk, Entergy would announce a leak of radiactive tritium into the groundwater from underground pipes that Entergy had sworn under oath didn’t exist.

“That created a firestorm throughout Vermont, and particularly in the Legislature, and definitely raised concerns of safety and reliability,” said Leppzer recently in his Turning Tide Productions editing studio. “When they announced the leak, they were caught in this lie, so there was also the issue of whether this corporation could be trusted.”

In one of his countless trips to Montpellier for this project, Lepper filmed a rally at the Capitol at which then- state Senator Peter Shumlin said he would support shutting down the 540-megawatt reactor. He went on become governor with a large anti-nuclear vote.

“Power Struggle” follows the Legislature’s investigations into whether Entergy had been covering up, including scenes with nuclear-engineer whistleblower Arnold Gundersen in which he testified that he’d been “stonewalled” by the company.

“We were told crystal clear that there were no buried underground pipes that contain radioactivity,” Gundersen told legislative panel as Leppzer filmed in the Statehouse “pretty much nonstop” for nearly all of that February. “I asked for a … report, I got it and I’m reading it and I said, ‘Oh my God, there’s buried and underground pipe!’”

The inquiry led to the state Senate’s 26-4 vote against allowing the state’s Public Service Board to extend the plant’s operation after March 21, 2012.

The NRC agreed to a 20-year license extension for the Vernon reactor on March 10, 2011 — just one day before the meltdown of three reactors at Japan’s Fukushima Daiichi plant. Those reactors were identical to the General Electric Mark 1 boiling-water reactor that Gundersen had long criticized as having serious design flaws.

The Fukushima accident — the cleanup costs for which have been estimated by Japanese college professors at more than $100 trillion — drew more than 500 protesters to the Vermont Yankee plant a week after it occurred.

“Power Struggle” also includes scenes and interviews with Australian anti-nuclear activist Helen Caldicott, Vernon neighbors and supporters of the plant as well as Massachusetts activists Frances Crowe, Hattie Nestel, Randy Kehler and Betsy Corner being arrested for civil disobedience.

“I think it should be shut down,” Crowe, who was 93 at the time and at 97 is scheduled to be honored with a tribute at the Northampton screening, told the district court judge at the trespass trial of her affinity group. “I’m trying to activate the citizens, I understand why a lot of people don’t protest. Young people have jobs, families, but older people, I want them to join me at the gate and say ‘no’ with their body. The system is totally rigged. There’s no way even the people working in it can bring about changes. It’s flawed, rigged to the core so the only way is for mass civil disobedience.”

Mass protests were stepped up after a January 2012 U.S. District Court ruled against the state in Entergy’s suit over the Vermont Legislature’s authority to prevent a license extension. The film records 1,500 protesters marching on Entergy’s Brattleboro offices on March 22, one day after the plant’s original license expired, with 136 people arrested for trespass as they call for the plant to be shut down.

Leppzer’s documentary also follows the legal appeals by both the State of Vermont and Entergy of the lower federal court’s mixed ruling, ultimately upholding the Vermont PSB’s authority to issue a certificate to keep the plant operating.

But two weeks after that final ruling came down in August 2013, Entergy announced its decision to shut the plant down when it finished its fuel cycle, at the end of 2014.

Although Entergy CEO William Mohl explained that its decision was purely because of financial considerations, Gundersen tells the camera, “Vermont Yankee was going to need about 250 million dollars of repair and replacement over the next two or three years to keep running and Entergy didn’t want to spend that money. So they pulled the plug on Vermont Yankee for economics, but it was economics under the scrutiny of a smart electorate who had kept themselves informed for the last 10 years.”

Leppzer, who continued to film Vermont Yankee Decommissioning Citizens Nuclear Advisory Panel meetings reviewing plans to build storage casks for high-level waste that will remain on site for decades, ends the film after the plant’s Dec. 29, 2014 closure. Left hanging are questions over decommissioning up to 60 years from now and long-term storage of that highly radioactive material.

“I definitely felt like I was on a roller coaster throughout the project,” says the filmmaker, who shot more than 700 hours of film for the 104-minute documentary.

The film, which includes comments from officials from Entergy, from the NRC and Vermont agencies that played a unique role in an issue in which the federal government has given itself exclusive jurisdiction, is an examination of the possibilities — and limitations — of citizens to have a say about nuclear power.

“This is a story of grass-roots democracy working, and the power of citizens to have a voice,” says Leppzer. “On the other hand, the reality is that Vermont Yankee is going to be a high-level nuclear waste dump indefinitely into the future. … It’s going to stay on the banks of the Connecticut River for decades, at least.”